# Rearranging a fomula??

• Apr 18th 2009, 02:43 AM
soc86
Rearranging a fomula??
How do i rearrange this fomula so N is the answer, i knw the answer is 11, but i'am struggling to rearrange the formula, and advise?

D = (I-S)/ N
(3995-145) / ? = 350

N=
• Apr 18th 2009, 02:50 AM
Air
Quote:

Originally Posted by soc86
How do i rearrange this fomula so N is the answer, i knw the answer is 11, but i'am struggling to rearrange the formula, and advise?

D = (I-S)/ N
(3995-145) / ? = 350

N=

You have to use general arithmetic rules. If you are not able to work it out then it's best to do it step by step. Remember, if you do one arithmetic operation on one side, it has to be done on the other side.

$\displaystyle D = \frac{I-S}{N}$

Multiply Both sides by $\displaystyle N$:

$\displaystyle DN = I - S$

Divide Both sides by $\displaystyle D$:

$\displaystyle N = \frac{I-S}{D}$

From here, you are able to substitute your numbers. It's best to re-arrange your formula first before inserting the numbers as if the numbers are decimals or fractions, it can make the re-arrangement more complicated.